The type-digits package

Arbitrary ype-level digits, for when the radix itself doesn't
actually matter. It's currently base-128, because that seemed to best
expedite the compilation of the modules using this package. Please let me
know what you find if you experiment with this.
Type.Digits.radix is the (arbitrary) radix. Type.Digits.digit computes
the NameG of a digit from its value (assuming its less than the
radix). Combinators are provided to compute a full type-level numeral from
values (potentially) larger than the radix.